The invention relates to machines for making hot beverages, especially to coffee making machines, and more particularly to improvements in adapters which can be used in conjunction with such machines for the preparation of cappuccino, i.e., espresso coffee or regular coffee with a topping of foamed or frothed milk.
An espresso making machine is normally provided with a conduit which serves to supply a stream of pressurized steam. Steam which is supplied by the conduit can be used to foam a supply of milk, such as a supply of hot milk in a cup or a similar vessel, for the purpose of using foamed milk as a topping for hot coffee or espresso in a regular cup or in a demitasse. The topping can be garnished with fragments of chocolate, ground coffee beans or in any other suitable way.
Published German patent application No. 36 44 519 discloses an adapter which has a rigid body provided with a first inlet for reception of a nozzle at the lower end of the steam-supplying conduit in an espresso making machine, a second inlet which receives the discharge end of an air supplying pipe, and an outlet which discharges a mixture of air and steam into a supply of milk in a suitable vessel. The flow of pressurized steam draws air by way of the pipe, and such air is supposed to be mixed with air prior to leaving the adapter by way of the outlet. The body of the adapter defines a relatively small mixing chamber which communicates with the two inlets and with the outlet and into which the inflowing pressurized steam draws an air stream by way of the air supplying pipe. An advantage of the just described adapter is that the internal surfaces of the body remain largely free of deposits of milk because pressurized steam normally prevents penetration of milk into the chamber by way of the outlet, even if the body of the adapter is fully immersed into milk. This is desirable because deposits of milk along the surfaces surrounding the mixing chamber, the inlets and/or the outlet could adversely influence the rate of inflow of air and steam as well as the rate of outflow of steam-air mixture and could reduce the effective volume of the mixing chamber.
The body of the adapter which is described in the published German patent application is a separately produced part which is connected to the nozzle at the lower end of the steam-supplying conduit. Such body resembles a funnel and is secured to a conical nozzle at the lower end of the steam-supplying conduit. As a rule, the body is bonded to the steam-supplying conduit by a suitable adhesive so that the conduit and the adapter constitute an integral unit. A separately produced adapter is preferred because this enables the manufacturer to make the steam-supplying conduit of a first material which is best suited for repeated contact with steam, and to make the body of the adapter of a second material, e.g., a material which is less likely to gather layers of incrustated milk. Moreover, the shape of a separately produced adapter body can be selected practically at will.
A drawback of the aforedescribed adapter is that it is permanently affixed to the steam supplying conduit. This not only necessitates the use of a suitable adhesive but also renders it necessary to select the materials of the steam-supplying pipe and of the adapter body with a view to ensure that they can be reliably bonded to each other. In addition, the application and setting of adhesive take up much time to thus prolong the assembly of the adapter with the coffee making machine. Still further, it is rather difficult to adequately clean the adapter for the purpose of removing eventual deposits of milk, and the adapter draws air at times when mixing of air with steam is not desirable or necessary. It is especially difficult to adequately clean the internal surfaces surrounding the mixing chamber and the outlet because the body of the adapter is permanently affixed to the steam-supplying conduit.
Paoletti U.S. Pat. No. 4,735,133 discloses a milk emulsifying device wherein milk, air and steam are mixed in a vacuum chamber. A drawback of the patented device is that its interior is invariably contaminated with milk whenever the device is put to use.
Commonly owned U.S. patent applications Ser. Nos. 205,114 (filed June 9, 1988) and 242,715 (filed Sept. 9, 1988) disclose a cappuccino making adapter which is more or less permanently affixed to the steam-supplying conduit of an espresso maker or a like machine. The adapter is equipped with a valve which can prevent admission of air when steam issuing from the conduit is to be used for purposes other than frothing milk. The adapter comprises a substantial number of parts.